Remote ischemic per-conditioning (RIPerC), the use of sub-lethal remote transient ischemia during lethal organ ischemia and prior to reperfusion, has been proposed as a novel therapy for ischemic events. It has been found effective in animal models of myocardial infarction (MI) and was also effective in a randomized clinical trial in MI. There are also recent reports of the efficacy of RIPerC in rodent stroke models with mechanical occlusion and reperfusion. These encouraging findings suggest that RIPerC may be a promising treatment for acute stroke. Therefore, it is important to test and optimize the effectiveness of RIPerC therapy in a physiological stroke model and to test with and without IV-tPA in aged animals of both sexes. To better model human stroke, we developed a physiological and clinically relevant partially- humanized mouse embolic model of stroke and have validated it in aged male and female animals. Our long term goal is to develop an inexpensive, safe therapy for stroke that could be used in all types of clinical settings, and in combination with IV-tPA. Ou preliminary data in an embolic MCAO clot model shows that RIPerC reduces the ischemic injury alone in young male mice and potentiated the benefits of late tPA therapy after stroke. Our specific aims are: AIM 1: Optimize the effective regimen of RIPerC alone and in combination with remote ischemic post-conditioning (RIPostC) to potentiate the benefits of IV-tPA treatment in young males and to investigate the short and long term functional outcome. We will optimize the most effective regimen of RIPerC therapy with/without RIPostC. We will use young males to determine the optimal regimen that we will test in aged animals of both sexes in Aim 2. We will measure cerebral blood flow, functional outcomes, infarct size and hemorrhagic transformation. Aim 2: Determine the effectiveness of the optimized remote conditioning regimen in combination with IV-tPA to investigate the long term benefits in aged male and reproductively senescent female mice (~18 months old). In this aim, we will investigate daily mortality and long term functional outcome on a battery of behavioral tests. We will also measure the injury size at day 28. These results will lay the groundwork for a UO1 submission with further milestones of efficacy in a larger animal model (pig) and in a rabbit embolic clot model and the eventual submission of an IDE for an early phase clinical trial in acute ischemic stroke.